This is the first application filed for the present invention.
This invention relates to the field of stand-alone renewable energy sources. More precisely, this invention relates to the field of renewable energy sources using hydrogen.
The last few years have seen the development of renewable energy (RE) systems, mainly wind-based and/or solar-based systems. These renewable energy systems are intended to help fighting against energy pollution and resource depletions.
A major issue in the renewable energy (RE) systems is the increase of the efficiency of energy conversion systems in order to optimize the use of currently available energy sources and at the end the extend to the use of other energy vectors.
Such systems are especially relevant to off-grid communities, usually located in remote areas (G. D. Rambach, xe2x80x9cIntegrated hydrogen utility systems for remote northern communitiesxe2x80x9d, 10th Canadian Hydrogen Conference, Quebec, Canada, May 2000; T. K. Bose, K. Agbossou, P. Bxc3xa9nard, J. M. St-Arnaud, xe2x80x9cNouvelles perspectives des systxc3xa9mes à xc3xa9nergies renouvelables basxc3xa9s sur l""hydrogxc3xa9nexe2x80x9d. 15e Confxc3xa9rence et exposition de l""Association canadienne d""xc3xa9nergie xc3xa9olienne, Rimouskixe2x80x94Canada, September 1999.).
These renewable energy (RE) systems are highly transient energy sources and exhibit strong variations in their energy outputs. Thus, they require proper means to store the energy produced in period of low demand in order to stabilize the output when the demand is high. At present, the storage of the excess energy relies mostly on batteries (Fisher, Jr., xe2x80x9cApparatus and method for charging an energy storage sourcexe2x80x9d, U.S. Pat. No. 6,194,793, Feb. 27, 2001; S. Mituo, S. Tsutomu, O. Hidekiyo, M. Hisafumi, xe2x80x9cPower supply apparatus for efficiently utilizing battery and electronic apparatus using the power supplyxe2x80x9d, U.S. Pat. No. 5,610,450, Jun. 29, 1995; T. O. Kent, B. Arthur J., xe2x80x9cMethod of power management for a hybrid powertrain systemxe2x80x9d, U.S. Pat. No. 5,999,864, Apr. 23, 1997). Batteries typically lose 1-5% of their energy content per month.
A better approach for excess energy storage is to produce hydrogen and store it in a clean renewable form (S. R. Vosen, J. O. Keller, xe2x80x9cHybrid energy storage systems for stand-alone electric power systems: optimization of system performance and cost through control strategiesxe2x80x9d, International Journal of Hydrogen Energy, vol. 24, 1999, p. 1139-1156; F. Menzl, M. Wenske, J. Lehmann, xe2x80x9cHydrogen production by windmill powered electrolyserxe2x80x9d, Hydrogen Energy Progress XII, vol. 1, 1998, p. 757-765; R. Pxc3x6tter, R. Pruschek, xe2x80x9cExamination of the design of the energy management for the PV plant PHOEBUS Jxc3xclich by dynamic programmingxe2x80x9d, Hydrogen Energy Progress XI, vol. 2, 1996, p.1185-1190).
An energy conversion device, such as a hydrogen fuel cell or an internal combustion engine (ICE) coupled with a co-generator can be used to convert back into electricity and heat (H. Barthels, W. A. Brocke, K. Bonhoff at al., xe2x80x9cPHOEBUS Jxc3xclich: An autonomous energy supply system comprising photovoltaic, electrolytic hydrogen, fuel cellxe2x80x9d, Hydrogen Energy Progress XI, vol. 2, 1996, p. 1005-1015; M. I. Ibrahim, A. A. Elmallah, M. H. Badr, A. S. Hanafi xe2x80x9cInvestigation of techno-economical performance of using hydrogen storage with integrated renewable energy systemsxe2x80x9d, Hydrogen Energy Progress XI, vol. 2, 1996, p. 2055-2060; Saeki Mituo, Suzui Tsutomu, Ozawa Hidekiyo, Mitsui Hisafumi xe2x80x9cPower-supply apparatus for efficiently utilizing battery and electronic apparatus using the power supplyxe2x80x9d, U.S. Pat. No. 5,999,864, Apr. 23, 1997; P. Hollmuller, J. M. Joubert, B. Lachal, K. Yvon, xe2x80x9cEvaluation of a 5 kWF photovoltaic hydrogen production and storage installation for a residential home in Switzerlandxe2x80x9d, Hydrogen Energy Progress XII, vol. 1, 1998, p. 423-443). The hydrogen produced, in excess of the system""s requirement, can be used to power other systems or in case of large-scale systems, it could be exported for use in the process industry.
There is a need for an apparatus that will overcome the limitations of the renewable energy system from the prior art.
It is an object of the invention to provide an apparatus for controlling a renewable energy system based on hydrogen.
It is another object of the invention to provide a method for providing stability in a two-independent-variable environment.
Yet another object of the invention is to provide a method for controlling power in a renewable energy system based on hydrogen.
According to a first aspect of the invention, there is provided an energy stand-alone supply providing electrical power to a load having an electrical power need using an energy supply source providing a source electrical power, wherein a time-variable discrepancy between said source electrical power provided by said energy supply source and said electrical power need, the energy stand-alone supply maintaining the provided electrical power between two values, the energy stand-alone supply comprising a buffer receiving a source electrical power from an energy supply, the buffer further providing electrical power to a load according to an electrical power need of said load, a first power converter connected to said buffer and providing a converted electrical power using at least one part of the source electrical power in response to a first control signal, a hydrogen generator receiving said converted electrical power and generating hydrogen using said provided converted electrical power, a hydrogen storage storing the generated hydrogen provided by said hydrogen generator, a hydrogen conversion device receiving at least one part of said hydrogen of said hydrogen storage and providing a generated electrical power in response to a second control signal, a second converter receiving said generated electrical power and providing a converted electrical power of the generated electrical power to said buffer and a control unit providing said first and second signal, the control unit enabling the maintaining of the provided electrical power between the two values according to a control scheme.
According to a second aspect of the invention, there is provided a method for providing electrical power to a load having an electrical power need using an energy supply and maintaining the provided electrical power between two values, wherein a time-variable discrepancy exists between said electrical power provided by said energy supply and said electrical power need of the load, the method comprising the steps of measuring an electrical power need of a load and an available electrical power of an energy supply, comparing said electrical power need of the load to said available electrical power of the energy supply to provide a comparison value, if said comparison value is larger than a first predetermined value, operating a hydrogen conversion device to provide extra electrical power using hydrogen stored in a hydrogen storage, the operating increasing the available electrical power, the operating being performed until said available electrical power reaches the electrical power need of the load, if said electrical power need of the load is lower with respect to said available electrical power of the energy supply by a second predetermined value, switching on a hydrogen generator, the switching on of the hydrogen generator providing hydrogen to the hydrogen storage, the switching on decreasing the available electrical power, the switching on being performed until said available electrical power reaches the electrical power need of the load, whereby the operating of the hydrogen generator and the switching on of the hydrogen conversion device enable the maintaining of the available electrical power between the two predetermined values.